THE South African pianist Abdullah Ibrahim played so quietly at his Royal Festival Hall concert that he seemed to be accompanied not only by the bass and drums of his own trio but by an orchestra of coughs from the audience. In a virtuoso performance of a type encountered only rarely outside the school assembly hall, the acoustics of the venue fairly fibrillated with the sound of thousands of throats being cleared in what must have been an instinctive nervous response to Ibrahim's very piano piano. Playing in a tent at Womad the previous night, the master had been forced reluctantly to turn up the volume knob, but here he remained as quiet as a mouse almost throughout.

Ibrahim has been playing like this for years now, with the result that you often hear the intestinal rumblings of the person sitting next to you more than you hear the music. In part, it's a fitting acoustic analogue to his austere, meditative approach (though in the past, he used to bash the keys good and proper), forcing the audience really to concentrate and listen. It's a kind of wily stagecraft: if we grow accustomed to the near-silence of the early numbers, then the heavy rumblings from the keyboard in the closing sequence will be all the more effective. And they are. By the end we were all caught up in Ibrahim's spell, and he left the stage to thunderous applause.

There remained a suspicion, however, that Ibrahim's velvet-glove approach might conceal a diminishing technique. His once harshly percussive style has been replaced by what too often sounds like tentative noodlings in the narrow band-width of the piano's middle registers, and even his familiar repertoire of hymn-like, deeply emotional compositions was only rarely apparent. The band - with the superb drummer George Gray, and Beldon Bullock on bass - were like greyhounds straining at Ibrahim's very tight leash. Gray got a run around the park once or twice, mixing his Township shuffle- rhythms with some almost drum-and-bass snare patterns, but he mostly had to restrict his inventiveness to some nifty drumstick twirling.

At the end, it was hard not to be moved, for Ibrahim's music - almost uniquely in contemporary jazz - is always likely to tug at the heart-strings and the tear-ducts. But for real noise, energy and joy we had to wait for the 10-strong vocal group Ladysmith Black Mbazo who both ended and stole the show. Famous for the song "Homeless" from Paul Simon's Graceland, the group combine close harmony singing in the Zulu tradition with knock- 'em-dead choreography. If the performance perhaps promised to be a bit on the worthy side, it turned out to be a barrel of laughs. Gorgeous singing, athletic high kicks, and a pleasingly democratic approach to the hierarchy expected from either a choir or a chorus-line combined to make Ladysmith Black Mbazo a huge hit. After the three encores, you left the hall with a spring in your step and a lump in your throat; not a bad combination.